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Power conversion device

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Power conversion device


The present invention aims to provide a power converter with an arm including switching devices connected in parallel, realizing long lifespans of switching devices. An inverter includes an upper and a lower arm, and gate drive circuits each driving the corresponding arm according to a gate control signal Gup_s indicating ON/OFF periods. Each arm includes switching devices connected in parallel. Each gate drive circuit includes: a switching gate control circuit 230u bringing a switching device 210u into conduction at the beginning of the ON period and bringing the same out of conduction within the ON period; and a conduction gate control circuit 231u bringing switching devices 211u and 212u within a period from when the switching device 210u is brought into conduction until the same is brought out of conduction, wherein the switching device 210u has a lower parasitic capacitance than the switching devices 211u and the 212u.

Inventor: Masaki Tagome
USPTO Applicaton #: #20120307540 - Class: 363131 (USPTO) - 12/06/12 - Class 363 


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The Patent Description & Claims data below is from USPTO Patent Application 20120307540, Power conversion device.

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TECHNICAL FIELD

The present invention relates to a power converter such as an inverter and a DC/DC converter having an arm composed of a plurality of switching devices connected in parallel.

BACKGROUND ART

In recent years, power converters such as inverters and DC/DC converters have increased their output power for the use in hybrid electric vehicles, electric vehicles, and the likes. In a high-output power converter, switching devices constituting an arm are required to manage high voltage and high current. To support high voltage, the switching devices are connected in series, and to support high current, the switching devices are connected in parallel. For example, Patent Literature 1 discloses an inverter having an arm composed of a plurality of switching devices connected in parallel.

CITATION LIST Patent Literature

[Patent Literature 1] Japanese Patent Application Publication No. 2005-6412

SUMMARY

OF INVENTION Technical Problem

When switching devices are connected in parallel, it is likely that a large amount of current flows in a particular device due to variations in the electrical properties of the devices. Hence, the device in which a larger amount of current flows generates a large amount of heat, and the lifespan of the device is likely to be short. In particular, parallel connection is more problematic during the switching operation than during the regular operation. That is, in addition to the variations in the electrical properties (e.g. on-resistance, threshold voltage), the difference in the junction temperature, the difference in the wiring inductance, and variations in properties of the gate drive circuits have an influence during the switching operation, and when compared with the case of a single device, the problem of variations is more significant in the case of the switching operation.

The present invention is made in view of the problems above, and aims to provide a power converter having an arm composed of a plurality of switching devices connected in parallel and realizing long lifespans of the switching devices.

Solution to Problem

To achieve the aim, the present invention provides a power converter comprising: an upper arm; a lower arm; and gate drive circuits each configured to drive a corresponding one of the arms according to a reference signal, the reference signal having a first-potential period and a second-potential period, wherein each arm includes a set of switching devices connected in parallel, each gate drive circuit includes: a switching gate control circuit configured to bring a first switching device among the corresponding set of switching devices at the beginning of the first-potential period, and to bring the first switching device out of conduction at a point within the first-potential period; and a conduction gate control circuit configured to bring a second switching device among the corresponding set of switching devices into conduction at a point within a period from when the first switching device is brought into conduction, which corresponds to the beginning of the first-potential period, until the first switching device is brought out of conduction, and the first switching device has a smaller parasitic capacitance than the second switching device.

Advantageous Effects of Invention

In the power converter pertaining to the present invention with the structure described in Solution to Problem, among the switching devices included in the arm, the switching loss occurs in the first switching device which performs the switching operation, and the conduction loss occurs in the second switching device which performs the conduction operation.

Hence, in the first switching device, heat caused by switching loss is generated, but heat caused by conduction loss is suppressed. In the second switching device, heat caused by conduction loss is generated, but heat caused by switching loss is suppressed. Therefore, the switching devices are prevented from having a short lifespan due to heat generation.

Conduction loss and switching loss, which are power loss occurring in switching devices and are recognized as common properties of switching devices, have a trade-off relationship. That is, a switching device with a reduced conduction loss has a relatively large switching loss, and a switching device with a reduced switching loss has a relatively large conduction loss.

In the power converter pertaining to the present invention, however, switching loss and conduction loss occur in different switching devices. Hence, switching loss and conduction loss, which conventionally have a trade-off relationship, can be each reduced in terms of the entire apparatus. That is, the present invention provides a highly efficient power converter that can reduce both types of loss in terms of the entire apparatus.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows the entire structure of a synchronous motor drive system using a power converter pertaining to the present invention.

FIG. 2 is a waveform diagram showing switching operations performed by an upper arm and a lower arm of an inverter.

FIG. 3 shows detailed structures of a gate control circuit and an arm of an inverter pertaining to Embodiment 1.

FIG. 4 is a timing chart illustrating operations performed by a gate control circuit.

FIG. 5 shows the current-voltage characteristic of a switching device.

FIG. 6 shows detailed structures of a gate control circuit and an arm of an inverter pertaining to Modification 1 of Embodiment 1.

FIG. 7 shows detailed structures of a gate control circuit and an arm of an inverter pertaining to Modification 2 of Embodiment 1.

FIG. 8 shows detailed structures of a gate control circuit and an arm of an inverter pertaining to Modification 3 of Embodiment 1.

FIG. 9 is a timing chart illustrating operations performed by a gate control circuit pertaining to Modification 3.

FIG. 10 shows detailed structures of a gate control circuit and an arm of an inverter pertaining to Modification 4 of Embodiment 1.

FIG. 11 illustrates mechanism by which a lower arm 22u malfunctions due to a turning on of a upper arm 21u.

FIG. 12 shows detailed structures of a gate control circuit and an arm of an inverter pertaining to Embodiment 2.

FIG. 13 is a timing chart illustrating operations performed by a gate control circuit of an inverter pertaining to Embodiment 2.

FIG. 14 shows detailed structures of a gate control circuit and an arm of an inverter pertaining to Embodiment 3.

FIG. 15 shows operations of gate control circuit in an inverter pertaining to Embodiment 3 and switching operations thereof.

FIG. 16 shows detailed structures of a gate control circuit and an arm of an inverter pertaining to Embodiment 3.

FIG. 17 shows detailed structures of a gate control circuit and an arm of an inverter pertaining to Embodiment 4.

FIG. 18 shows the entire structure of a synchronous motor drive system using an inverter pertaining to Embodiment 5.

FIG. 19 shows a positional relationship between an arm and a capacitor of the inverter pertaining to Embodiment 5.

FIG. 20 shows detailed structures of a gate control circuit and an arm of an inverter pertaining to Embodiment 6.

FIG. 21 compares voltage-current characteristics in saturation regions of IGBT and MOSFET.

FIG. 22 shows the entire structure of a synchronous motor drive system using a DC/DC converter pertaining to the present invention.

FIG. 23 shows detailed structures of an arm 81 and a gate drive circuit 83 depicted in FIG. 22.

DESCRIPTION OF EMBODIMENTS

The following describes embodiments of a power converter pertaining to the present invention, with reference to the drawings.

Embodiment 1

FIG. 1 shows the entire structure of a synchronous motor drive system using a power converter pertaining to the present invention.

The synchronous motor drive system shown in the drawing includes a battery 1, an inverter 2 as a power converter pertaining to the present invention, a motor 3, and a control circuit 4.

The battery 1 is a DC power source, and supplies DC power to the inverter 2.



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Next Patent Application:
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stats Patent Info
Application #
US 20120307540 A1
Publish Date
12/06/2012
Document #
13576736
File Date
02/04/2011
USPTO Class
363131
Other USPTO Classes
International Class
02M7/537
Drawings
24



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